The tufting industry has long sought easy and efficient methods of producing new visual patterns on tufted fabrics. In particular, the industry has sought to tuft multiple colors so that any selected yarns of multiple colors could be made to appear in any desired location on the fabric. Significant progress toward the goal of creating carpets and tufted fabrics selectively displaying one of a plurality of yarns came with the introduction of a variety of servo motor driven yard feed attachments. Notable among these attachments are the servo scroll attachment described in Morgante, U.S. Pat. No. 6,224,203 and related patents; the single end servo scroll of Morgante, U.S. Pat. No. 6,439,141 and related patents; and the double end servo scroll of Frost, U.S. Pat. No. 6,550,407.
In operation the servo scroll yarn feed attachment, when alternating needles are threaded with A and B yarns respectively, allows the control of tufting of heights of yarns so that at a given location on the surface of the tufted fabric, either or both of the A and B yarns may be visible. However, a servo scroll yarn feed carries several yarns on each servo driven yarn feed roll so that the pattern must repeat several times across the width of the fabric and a yarn tube bank must be used to distribute the yarns. The implementation of the single end scroll pattern attachment, and the similar double end servo scroll pattern attachment, permitted the tufting machine to be configured with A and B yarns fed to alternating needles on a front needle bar while C and D yarns were fed to alternating needles on a rear needle bar in order to create color representations on tufted fabrics. The single end scroll yarn feed could create patterns that extended across the entire width of the backing fabric. However, in the full color application described above, these efforts suffered from the difficulty that if a solid area of one color was to be displayed, only one of every four stitches was tufted to substantial height and the remaining three colors were “buried” by tufting the corresponding yarn bights to an extremely low height. With only one of four stitches emerging to substantial height above the backing fabric, the resulting tufted fabric had inadequate face yarn for general acceptance.
The principal alternative to these servo yarn drive configurations has been the use of a pneumatic system to direct one of a plurality of yarns through a hollow needle on each stitch of tufting machine, as typified by U.S. Pat. No. 4,549,496. Such hollow needle, pneumatic tufting machines were traditionally most suitable for producing cut pile tufted fabrics and have been subject to limitations involving the sizes of fabrics that can be tufted, the production speed for those fabrics, and the maintenance of the tufting machines due to the mechanical complexity attendant to the machines' operation. Accordingly, the tufting industry has had a long felt need for a tufting machine that could operate efficiently to display one of several yarns at a selected location while maintaining a suitable density of yarns and operating at speeds approaching those of conventional tufting machines.
It should be noted that the pneumatic tufting machines utilizing hollow needles as in U.S. Pat. No. 4, 549,496 generally tuft laterally for between about one-half to four inches before backing fabric is advanced. Because the yarn being tufted is cut at least every time the color yarn being tufted through a particular needle is changed, there is no unnecessary yarn placed as back stitches on the bottom of the tufted fabric. However, when attempts have been made to utilize a regular tufting machine configuration with a needle bar carrying a transverse row of needles in a similar fashion, the yarns are not selected for tufting and cut after tufting, but instead each yarn is tufted in every reciprocal cycle of the needle bar. Therefore yarn carrying needles all penetrate the backing fabric on every cycle. The yarns are selected for display by a yarn pattern device feeding the yarn to be displayed and backrobbing the yarns that are not to be visible thereby burying the resulting yarn bights or tufts very close to the surface of the backing fabric. If several stitches are made as the needle bar moves laterally with respect to the backing fabric, then back stitch yarn for each of the colors of yarn is carried for each stitch and this results in considerable “waste” of yarn on the bottom of the resulting tufted fabric. Independently Controlled Needle (ICN) tufting machines typified by Kaju, U.S. Pat. No. 5,392,723 and related patents operate similarly, except the selection of the needles determines the yarns that will be displayed.
To overcome these difficulties, three methods of configurating and operating tufting machines of conventional design have been devised for the placement of color yarns.
In a first alternative, a pile fabric can be created selectively displaying one of three or more distinct yarns in the following fashion. Using the example of a thread-up featuring four yarns that have distinct colors, an inline needle bar, typically of about 1/10th gauge is threaded with a repeat of A, B, C, D over every four needles. The tufting machine is programmed to tuft four stitches laterally before advancing the backing fabric. In this fashion, each of the four adjacent needles threaded with yarns A, B, C, and D respectively will penetrate the backing fabric at nearly the same position. On those four cycles of the needles penetrating the backing fabric, adequate yarn will be fed by the associated servo motor for the color that is desired to predominate visually in that location. Sufficient yarn is fed to allow the yarn bight of the desired color to be tufted at a relatively high level. The other yarns are backrobbed in order to bury their associated yarn bights at a relatively low level. After tufting the four lateral cycles, the backing fabric is advanced and the four lateral stitch cycle is repeated with the needle bar moving in the opposite direction. It can be seen that this method, although functional, results in excess yarn on the bottom of the tufted fabric compared to ordinary tufted fabrics, and requires that the tufting machine operate only at about one-fourth the speed that it would operate if tufting conventional fabric designs. This technique was described in U.S. Pat. No. 8,141,505 to Hall, and will be discussed in further detail below.
In a second alternative it is possible to create a similar color placement effect in a cut/loop pile fabric utilizing the level cut loop configuration of U.S. Pat. No. 7,222,576 tufted on a tufting machine having about a 1/10th gauge needle bar with a four color repeating thread-up. The tufting machine is operated to tuft laterally four times and allows the color chosen for display to be either a cut or loop bight while backrobbing the yarn colors not to be shown on the face of the carpet, and leaving only very low tufts of those yarns. Obviously, three or more than four different yarns may be used in the thread-up with a corresponding adjustment in the number of lateral shifts. In this method of operation, there is again considerable excess yarn carried on the bottom of the backing fabric.
Both the first and second alternatives are essentially the same techniques that have been utilized with two colors of yarn on a widespread basis in the tufting industry in past years. Although multiple cycles of lateral shifting presents some issues not present when shifting only a single lateral step, the principal issue is one of avoiding overtufting or sewing exactly in the same puncture of the backing fabric made by a previous cycle of a nearby needle. This is typically addressed by using one or both of positive stitch placement and continuous, but reduced speed, backing fabric feed.
An additional problem presented by the first and second alternative techniques is the sheer number of penetrations of the backing fabric which results in degradation or slicing of nonwoven backing fabric materials that are commonly utilized in the manufacture of tufted fabrics for carpet tiles and special applications such as automotive carpets.
Finally, to overcome these shortcomings, a third alternative to produce similar fabrics with yarn placement has been achieved with a staggered needle configuration having front and rear rows of needles offset or staggered from one another. A staggered needle bar typically consists of two rows of needles extending transversely across the tufting machine. The rows of needles are generally spaced 0.25 inches apart in the longitudinal direction and are offset so that the needles in the rear transverse row are longitudinally spaced between the needles in the front transverse row. Alternatively, two sliding needle bars each carrying a single transverse row of needles may be configured in a staggered alignment.
In operation the needle bar is reciprocated so that the needles penetrate and insert loops of yarn in a backing material fed longitudinally beneath the needles. The loops of yarn are seized by loopers or hooks moving in timed relationship with the needles beneath the fabric. In most tufting machines with two rows of needles, there are front loopers which cooperate with the front needles and rear loopers which cooperate with the rear needles. In a loop pile machine, it may be possible to have two separate rows of loopers such as those illustrated in U.S. Pat. No. 4,841,886 where loopers in the front hook bar cooperate with the front needles and loopers in the rear hook bar cooperate with rear needles Similar looper constructions have been used in tufting machines with separate independently shiftable front and rear needle bars, so that there are specifically designated front loopers to cooperate with front needles and specifically designated rear loopers to cooperate with rear needles. To achieve maximum stitch density, and to minimize the possibility of tufting front and rear needles through the same penetrations of the backing fabric, it is desirable to offset the front loopers from the rear loopers by a half gauge unit.
The result of having loopers co-operable with only a given row of needles on a fine gauge tufting machine with two independently shiftable needle bars is that it is only possible to move a particular needle laterally by a multiple of the gauge of the needles on the relevant needle bar. Thus for a fairly common 0.20 inch (⅕th) gauge row of needles with corresponding loopers set at 0.20 inch gauge, the needles must be shifted in increments of 0.20 inches. This is so even though in a staggered needle bar with two rows of 0.20 inch gauge needles the composite gauge of the staggered needle bar is 0.10 inch gauge. The necessity of shifting the rows of needles twice the gauge of the composite needle assembly results in patterns with less definition than could be obtained if it were possible to shift in increments of the composite gauge.
One effort to reduce the gauge of tufting has been to use smaller and more precise parts. Furthermore, in order to overcome the problem of double gauge shifting, U.S. Pat. No. 5,224,434 teaches a tufting machine with front loopers spaced equal to the composite gauge and rear loopers spaced equal to the composite gauge. Thus on a tufting machine with two rows of 0.20 inch gauge needles there would be a row of front loopers spaced at 0.10 inch gauge and a row of rear loopers spaced at 0.10 inch gauge. Although this allows the shifting of each row of needles in increments equal to the composite gauge, this solution was limited in that the front needles can only be used to create loop pile and the rear needles can only be used to create cut pile.
Taking the arrangement of staggered needle bars shiftable at a composite gauge, and threading front needles with A and B yarns and rear needles with C and D yarns to form a repeat, a high volume of tufted fabric with selectively placed colored yarns can be manufactured with minimal wasted yarn used in the back stitching. This is because it is only necessary to shift each row of needles by a single lateral step in order to place all four A, B, C and D yarns in the desired location as described in U.S. Pat. No. 8,240,263. A principal disadvantage to this tufting arrangement and operation is the requirement for the use of twice as many needles and twice as many single end yarn drives as would be the case with slower and less efficient tufting arrangements for the selective placement of individual yarns. This results in increased cost and complexity of the tufting machine. Accordingly, improved methods of tufting machine operation to accomplish yarn color placement are still needed.